Re: [Xenomai-core] High latencies on ARM.

[Philippe Gerum <rpm@xenomai.org>]

Gilles Chanteperdrix wrote:
> On Jan 23, 2008 6:48 PM, Philippe Gerum <rpm@xenomai.org> wrote:
>> Gilles Chanteperdrix wrote:
>>> Gilles Chanteperdrix wrote:
>>>  > Please find attached a patch implementing these ideas. This adds some
>>>  > clutter, which I would be happy to reduce. Better ideas are welcome.
>>>  >
>>>
>>> Ok. New version of the patch, this time split in two parts, should
>>> hopefully make it more readable.
>>>
>> Ack. I'd suggest the following:
>>
>> - let's have a rate limiter when walking the zombie queue in
>> __xnpod_finalize_zombies. We hold the superlock here, and what the patch
>> also introduces is the potential for flushing more than a single TCB at
>> a time, which might not always be a cheap operation, depending on which
>> cra^H^Hode runs on behalf of the deletion hooks for instance. We may
>> take for granted that no sane code would continuously create more
>> threads than we would be able to finalize in a given time frame anyway.
> 
> The maximum number of zombies in the queue is
> 1 + XNARCH_WANT_UNLOCKED_CTXSW, since a zombie is added to the queue
> only if a deleted thread is xnpod_current_thread(), or if the XNLOCKSW
> bit is armed.

Ack. rate_limit = 1? I'm really reluctant to increase the WCET here,
thread deletion isn't cheap already.

-- 
Philippe.